Analytical Investigation of Gas Production from Methane Hydrates upon Thermal Stimulation

• Main Author: Roostaie, Mohammad
• Format: Master Thesis
• Language: English
• Published: University of Waterloo 2020
• Subjects: methane hydrate; dissociation; thermal stimulation; coaxial wellbore heat source; modeling; wellbore layers; Methane hydrate
• Online Access: http://hdl.handle.net/10012/15642

In this study, analytical models are developed to investigate methane hydrate dissociation in porous media upon thermal stimulation employing wellbore heating. This work investigates how the wellbore’s external and internal structure affect the dissociation process. The models are based on both Radial (2D) and Cartesian coordinates (1D) to couple the wellbore heating process and the associated methane response in the hydrate dissociation in the reservoir. Different types of heat-sources are studied: i) a flat heat-source in the 1D cases with a constant temperature; ii) line heat-source in radial cases with a constant temperature; iii) wellbore heat-source in radial cases, employing both a constant temperature and a coaxial wellbore. Wellbore’s external layers consist of casing, gravel, and cement. In the coaxial wellbore heat-source, both conduction and convection heat transfers are considered. It consists of an inner tube and an outer structure (casing, gravel, and cement layers). The analytical solution employed a similarity solution, in which a moving boundary to separate the dissociated (containing produced gas and water) and undissociated (containing only methane hydrate) zones is assumed, to model the dissociation in the reservoir. Two different operating schemes have been studied for water inlet of the coaxial wellbore heat-source: i) inner tube; and ii) annulus section of the wellbore. The results of temperature distribution along the wellbore (for the coaxial heat-source), temperature and pressure distributions in the reservoir, hydrate dissociation rate, and energy efficiency considering various initial and boundary conditions and reservoir properties are presented and compared with those of the previous studies. Direct heat transfer from the heat source to the reservoir in the case with a line heat-source higher dissociation rate and gas production compared to those of the wellbore-heat-source models, considering the heat conduction in the wellbore thickness causes. Decreasing the heat-source pressure ...